Radio receiving system



April 22,- 1924;- 1,491,372

E. F. W. ALEXANDERSON RADIO RECEIVING SYSTEM Fi led Oct. 28. 1921 PHASE I n 0rA T0)? Inventor: ErnstFM/Alex anderson,

His Attorngg.

Patented Apr. 22, 1924.

UNITED STATES-PATENT OFFICE.

ERNST I. W. ALEXANDERSON, OF SCHENECTA'DY, NEW YORK, ASSIGNOR TO GENERAL ELECTRIC COM'PANY, A CORPORATION OF NEW YORK.

' namo RECEIVING SYSTEM.

Application filed 0mm 28, 1921. Serial No. 511,127.

To all whom it may concern:

Be it known that I, ERNs'r F. W. ALEX- ANDERSON, a citizen of the United States, residing at Schenectady, in the county of- Schenectady, State of New York, have invented certain new and useful Improvements in Radio Receiving Systems, of which the following is a specification.

My present invention relates to systems for receiving high frequency radio signals, and more particularly to systems of this nature having a high degree of selectivity.

Selectivity in radio reception in the past has only taken into account the frequency of the signaling wave and the direction of wave'motion. By means of these two factors it is possible to eliminate to a large extent interference from undesired stations of different wave length, or stations having aproximately the same wave length, which are ocated in a different direction from the receiving station than the station from which signals are to be received. By means of.

these selective features it is also possible to eliminate to a large extent the effect of static disturbances, particularly those which are traveling in a different direction than the direction of the signaling wave. Another factor which, however, has not been employed for increasing selectivity and eliminating static disturbances is the phase of the signaling wave. While some static disturbances which may be of substantially the same frequency as the signaling wave may also be substantially in base therewith, the probabilities are that t e greater percentage of static disturbances are out of phase with the signaling wave. If, therefore, a receiving apparatus is constructed which is capable of discriminating between waves differing in phase and of selecting only currents which are in base with the signaling current a much higher degree of selectivity and freedom from static disturbances may be obtained.

The object of myinvention is to provide a simple and efficient radio apparatus which will have the property of discriminating between currentsdilfering in phase.

If a receiver is to respond only to impulses in phase with the signal, the phase used as reference must be established by integration over as long a period as possible. Any wave that has not a constancy of phase and amplitude or the duration of which is short in comparison with that of the signaling wave, Wlll not re 'ster in such a way as to form a definite p ase. If a wave train is not in phase w th the signal, it should'not produce any lndication. A receiver of the desired type, therefore, should have two elements; an lntegrating element which establishes the average phase of the signal, and a direct actmg element which records impulses in so far as such impulses are in phase with current established by the integrating element. Assume, for example, that a synchronous motor is driven by the audio frequency current of the signal. Assume further. that the motor drives a flywheel, and that the indicatlng device registers the torque transmitted by the motor to the flywheel. The flywheel would maintain an integrated phase but the torque reactions would register instantaneously. If disturbing currents are introduced into the driving system which are 90 out of phase with the integrating phase, they would produce no torque on the motor.

Any electrical equivalent of a mechanical device of this sort may be reduced by means of a sharply tuned ClI'Clllt, particularly of audio frequency, which acts as a flywheel. This circuit may form either the grid or plate circuit of a three-electrode electron discharge device, and the current to be detected may be simultaneously impressed upon both the grid and plate circuits of the device. If the two currents are in phase, current will be allowed to flow in the plate circuit and the device may be so adjusted that if the currents are 90 or more 'out of phase, no current will flow in the plate'circuit. Since the current in the flywheel circuit will be maintained in substantiallyconstant phase, currents in the other circuit which are out of phase will therefore pro-' duce no indication.

characteristic of my invention are set forth 1 with particularity in the appended claims;

' my invention itself, however, both as to its organization and method of operation, together with further objects and advantages thereof will best be understood by reference to the following description taken in connection with the accompanying drawing, in whichFig. 1 shows diagrammatically one way in which my invention may be carried into effect with radio frequency tuning; Fig. 2 shows a system in which audio frequency tuning is employed to secure the integrating effect; Fig. 3 shows a receiving system in which two antennae having different directive properties are employed and the principle of phase selection is utilized for securing sharper directivity; and Fig. 4 is a receiving diagram of the arrangement illustrated in Fig. 3.

As indicated in the drawing, I preferably employ in my receiving apparatus an electron discharge device 1 of the usual threeelectrode type having gi'id and plate cir cuits associated therewith. Signaling current received upon the antenna 2 is impressed, in the arrangement shown in Fig. 1, upon both the grid and plate circuits by means of the coupling transformers 3 and 4. The plate circuit is sharply tuned by means of a condenser 5 and the indicator 6 is associated with the plate circuit for the purpose of giving the desired indication of the received signals. Signaling current from the secondary of transformer 4 is supplied to the grid circuit of the device 1 through a phase rotator 7 for the purpose of so adjusting the phase of thesignaling current in thegrid circuit that it will be in phase with-the current'in the plate circuit. If the electron discharge device which is employed has sharp characteristics and the normal signal intensity is just sufficient to bring both grid and plate circuits up to the point where the tube becomes conductive when the plate and gridcircuits are in phase, then it is obvious that the signaling current .will readily pass through the tube, whereas any disturbances which are not in phase with the signaling current will not.

pass through unless they are of equal or greater strength than the signal. A phase selector of this simple form may be useful in connection with the operation of the recording device because. it will give a cleancut record when the disturbances are of a moderate intensity. vWhen, however, atmospheric disturbances are several times the intensity of the signal the flywheel efl ect which may be obtained in this manner will be insufficient to prevent the atmospheric disturbances from producing currents which are in phase in both the plate and grid circuits.

The grid of the device 1 is preferably given a negative bias by means of the bat.- tcry 8 as by this means the phase selectivity will be greatly increased. The combination of the effects of the two currents in this manner apparently follows an entirely diiferent law than the usual vectorial combination. For example, if two currents of unlike phase are combined vectorially they will give a resultant current unless they are 180 apart in phase; I find on the other hand, that with the combination described, the resultant current may be reduced to a zero value when the phase displacement between the two currents is 90, or even less.

In the arrangement shown in Fig. 2 of the drawing, the signaling currents received upon the antenna 2, if of continuous wave form, are combined with currents from a local source 9 to produce beats and the beat current is rectified by means of a rectifying detector 10. The currents thus produced are preferably of audio frequency and are impressed directly upon the plate circuit of device 1 and are impressed upon the grid circuit of device 1 through a coupling trans former 11. The grid circuit in this case is sharply tuned by means of condenser 12 to give a flywheel efl'ect. With this combination it is ap arent that only currents which are substantially in phase with currents in a grid or flywheel circuit will flow through the plate circuit and the indicator 6. The

signaling current will give a clear indication in the indicator 6 as long as it is applied to the plate circuit. The flywheel circuit will have a tendency to continue oscillating after the signaling current has been out off. This swinging of the flywheel circuit will not produce any sound in the receiver, however, because no voltage will be applied to the plate. By means of this arrangement successful operation may be obtained with disturbing impulses much stronger than the signal because the disturbances will be of indiscriminate phase and will not have the same accumulative effect in the flywheel circuit as the signal which is of constant phase and frequency. When no signal is being received the flywheel circuit will be comparatively inactive, no current will pass through the indicator and it will not be until the static disturbances have reached an intensity many times that of the signal that they will affect the flywheel circuit sufiiciently to allow current to flow through the indicator.

The principle of phase selection outlined above may be used to advantage in combining signals received from two stations of different geographical location or different directive characteristics. In Fig. 3 I have indicated a receiving system in which two directive receiving antennae 13 and 14 are employed which extend in directions approximately 90 from each other. The receiving diagrams of these two antennae overlap only to a slight extent, as indicated in the diagram of Fig. 4, the extent of overlapping being shown by the shaded area of the diagram. If the currents received from the two antennae were combined vectorially in the ordinary way, three diagramsceived only from the directions indicated by the shaded area of the diagram.

In the arrangement shown in Fig. 3, the two antennae are connected toseparate detectors 15 and 16. but both of the detectors are controlled by the same local heterodyne source 17 or its equivalent. Current from detector 15 is passed through the plate circuit of the device 1 while the current from the detector 16 is passed through the phase rotator 18 and supplied to the grid circuit of device 1. 7

If a wave is received from a direction which is not within the overlapping range of the two receiving diagrams, it will act only upon one of the detectors. It will, therefore, ati'ect only the plate circuit or the grid circuit of the phase selector, and neither of these actions will produce any sound in the telephone receiver 6. Upon the other hand, if a signal is received from a direction which is within the range of the overlapping of the directivity diagrams, the signal will act upon both detectors. The phase rotator 18 is so adjusted that signals from the desired direction will produce impulses which are in phase in the grid and plate circuits, and under these circumstances the signals will produce a sound in the tele-' phone receiver. It is apparent that by the means described much sharper directivity may be obtained than with a simple'directive antenna. The arrangement described is, of course, not entirely immune to the effects produced by impulses received .from the non-overlapping parts of the receiving diagram. If two disturbing impulses are received simultaneously one by one antenna and the other by the other antenna, these two disturbances will act simultaneously upon the grid circuit and the plate circuit of the phase selector. They will, however, produce no effects in the telephone unless they are in phase. Inasmuch as atmospheric disturbances are of indiscriminate phase, it is obvious that the greater part of these simultaneous disturbances will be eliminated. There may. however, be a residual of disturbances which occur simultaneously from different directions and which are in phase. as well as disturbances which come from the same direction as the signaling wave. The efiect of these disturbances may be largely overcome by introducing a flywheel tuning 19 in the grid circuit of the system shown in Fig. 3.

The form of my invention shown in Fig. 3 is described and claimed in my application Serial No. 638,362, which is a'continuation in part of the present application.

Current limiting devices may to advantage be employed in order to limit the current which can be supplied to the t1 Wheel circuit at any time to a value so stantially equal to the signaling current.

Any desired form of current limiting device may be used. For example. an electron discharge device having two filamentary electrodes 22, 23, with means for adjusting the heating currents thereof to such a value that the current flowing between the electrodes cannot exceed a predetermined de-' sired value may be inserted in series with the conductors 20, 21 of Fig. 2. The use of such a device will prevent shocking of the flywheel circuit by disturbances of large intensity and thereby causing the phase of the current therein to vary. While the use of such devices may also limit the signal at the time a severe static disturbance occurs, their use in this connection will not be objectionable because of the fact that the flywheel efiect will carry the current over the period when the ,current limiting device comes into action. Such devices, however, should not be employed in the circuit in which there is no flywheel effect, as they would tend to limit the signaling current to such an extent as to greatly reduce the signal strength whenever a severe dis turbance occurs; What I claim as new and desire to secure by Letters Patent of the United States, is

1. The combination in a signal receiving system of a detector, two circuits associated with said detector upon which received signaling current may be impressed, means associated with one of these circuits for integrating the phase of the signaling current flowing therein, an indicator associated with one of said circuits and means associated with the other circuit for causing said indicatorto respond only to currents which are in phase with the signaling current.

2. The combination in a signal receiving system of a detector, two circuits associated with said detector upon which received sig naling currents may be impressed, means associated with one of these circuits for maintaining substantially constant the phase of the current therein, an indicator associated with one of said circuits and means associated with the other circuit for causing said indicator to respond only to currents which are in phase with the current in the indicator circuit.

3. The combination in a signal receiving system of a detector, two circuits associated with said detector upon which received signaling currents may be impressed, one of sald circuits comprising a low decrement tuning to the signal frequency, an indicator associated with one of said circuits, and means associated with the second circuit for causing said indicator to respond only to currents which are in phase with the current in the second circuit.

4. The combination in a signal receiving system of a detector for producing an audio frequency current from the received high frequency-current, two 'separate'circuits asj'; sociated with said detector to which the audio frequency currents may be supplied,

means associated with one of said circuits for-integrating the phase of the signaling current, an'indicator associated with one of said circuits and means associated with the other circuit for causing said indicator to respond only to currents which are in phase with the signaling current.

5. The combination in a signal receiving system of a detector for producing an audio frequency current from the receivedhigh frequency current, two separate circuits associated with said detector to which the audio frequency currents may be supplied, means associated with one of .said circuits for maintaining substantially constant the phase of the current therein, an indicator associated with one of said circuits, and means associated with the second circuit for causing said indicator to respond only to currents which are in phase with the currents in the second circuit.

6. The combination in a signal receiving system of a detector for producing an audio frequency current from the received high frequency current, two separate circuits associated with said detector to which the audio frequency currents may be supplied, one of said circuits comprising a low decrement tuning to the audio frequenc signal current, an indicator associated wit one of said circuits and means associated with the second circuit for causing said indicator to respond only to currents which are in phase with the current in the second circuit.

7. The combination in'a si 'nal receiving system of detecting means or producin audio frequency currents from the receive high frequency currents, two separate circuits towhich the audio frequency currents are supplied, an indicator associated with one of said circuits, and means controlled by the current in the second circuit for causing said indicator to respond only to currents having a predetermined phase'relation to the current in the second circuit.

8. The combination in a signal receiving system of an. electron discharge device having plate and grid circuits associated therewith, means for supplying signaling currents to both of said circuits, means associated with one of said circuits for integrating the phase of the signaling current flowing therein, an indicator associated with the plate circuit, and means associated with the grid circuit for causing said indicator to respond only to currents in the grid circuit which are substantially in phase with the current in the plate circuit.

9. The combination in a signal receiving system of an electron discharge device having plate and grid circuits associated therewith, means for supplying signaling cur- 1,491,372 I p O rents to both of said circuits, one of said circuits comprising a low decrement tuning to the si al frequency, an indicator associated with the plate circuit, and means associated with the grid circuit for causing said indicator to respond only to currents in the grid circuit which bear a predetermined phase relation 'to he signal current in the plate circuit.

10. The combination in a signal receiving system of an electron discharge device having plate'and grid circuits associated therewith, means for supplying audio frequency signaling currents to both of said circuits, one of said circuits comprisin a low decrement tuning to the si al requency, an indicator associated wit the plate circuit and means associated with the grid", .,circuit for causing said indicator to respond only to currents in the grid circuit which bear a predetermined phase relation to the signal current in the late circuit.

11. The com ination in a signal receiving system of an electron discharge device having plate and grid circuits associated therewith, means for en plying signaling currents to both of said circuits, one of said circuits comprising a low decrement tuning to the signal frequency, an indicator associated with the late circuit, means associated with the gri circuit for causing said indicator to respond only to currents in the grid circuit which bear a predetermined phase relation to the signal current in. the plate circuit, and means for adjustin the phase of the current supplied to one 0 said circuits.

12. The method of selective reception of radio signals which consists in supplying received signaling currents totwo circuits, integrating the phase of the signaling current flowing in one of said circuits and controlling the response in an indicator in one of said circuits by means of current flowing in the other circuit in such a way that the indicator will respond only to signaling currents which are in phase with the current of integrated phase.

13. The method of selective reception of radio signals which consists in producin an audio frequency current from receive signaling currents, impressin the audio frequency currents upon two lifl'erent circuits, integrating the phase of the current in one of said circuits, and controllin the response of an indicator in one of sai circuits by means of the current in the other circuit in such a way that it will respond only to currents of the same phase as the current of integrated phase.

14. The method of selective reception of radio signals which consists in producing audio frequency currents from received signaling currents, impressing these audio frequency currents upon two difierent circuits,

Kid

not

integrating the phase of the current in one currents in the second circuit, which are in of said circuits, limitin the current which phase with the current of integrated phase may be supplied to "sai circuit to a value in the first circuit.

substantially equal to the maximum si nal In witness whereof, I have hereunto set 5 current, and controlling the response 0 an my hand this 22nd day of October, 1921.

indicator in the second circuit in such 'a way that the indicator will respond onlyto ERNST F. W. ALEXANDERSON. 

